Air springs are developed in correspondence to the particular characteristics required such as supporting force, spring characteristic and spring path. Basically, there are two types of air springs, namely, rolling-lobe air springs and bellows air springs.
The rolling-lobe air springs described below essentially include a flexible member to accommodate the spring movement and a roll-off piston. The flexible member is made of elastic material. The open ends of the flexible member are sealed off by attachment parts. During spring action, a rolling lobe of the flexible member forms and rolls on the roll-off piston.
Air springs having a flexible member defining a rolling lobe are of at least two types: the first type has a clampable sealing bead formed at the end of the rolling lobe. The second type has a conical sealing surface at the end of the rolling lobe. These types differ by the way in which they are clamped. The air spring of the invention includes a sealing bead which can be clamped.
The spring characteristic is essentially dependent upon whether or not the particular volume of the roll-off piston is to be included with the volume of the flexible member as a spring variable.
U.S. Pat. No. 4,506,910 discloses an air spring having a flexible member defining a rolling lobe.
The spring element should be configured to be especially soft when the air spring is subjected to an increase of the spring path because of a lever arm. This, however, is not the case in the above-mentioned air spring. The suspension is hard because the resilience of the spring is provided exclusively by the volume of the flexible member and not also additionally by the volume of the piston as is the case, for example, in the air spring shown in German Patent 3,147,231.
In the last-mentioned air spring, the formed sheet metal part which delimits the flexible member with respect to the plunge piston, has openings through which the volume of the flexible member and the volume of the plunge piston are connected to each other. In this way, a greater overall volume is obtained which provides a softer spring action. The flexible member described in German Patent 3,147,231 includes sealing beads at its upper and lower ends. The sealing beads are connected to the rigid parts of the air spring by means of a snap ring or by means of a formed sheet metal part.
U.S. Pat. No. 4,506,919 discloses an air spring wherein the flexible member is connected to the piston utilizing threaded fasteners. In air springs of this kind, it was not possible to connect the piston volume because the tightness between the flexible member and the volume of the piston could not be ensured.